The bongs of the iconic bell will be stopped after chiming noon on Aug. 21 to protect workers during a 29-million-pound ($38 million) repair project on the Queen Elizabeth Tower, which houses Big Ben and its clock. It isn't due to resume regular service until 2021.

Steve Jaggs, keeper of the Great Clock, said Monday that the clock mechanism will be dismantled piece by piece and its four dials will be cleaned and repaired. The 13.5 British ton (15.1 U.S. ton, 13.7 metric tons) bell will be cleaned and checked for cracks.

Big Ben has been stopped several times since it first sounded in 1859, but the current restoration project will mark its longest period of silence.

Parliamentary officials say they will ensure that the bell still sounds on major occasions, such as New Year's Eve and Remembrance Sunday.

The silence presents a problem for the BBC, which broadcasts the bongs every evening before the radio news through a microphone in the belfry.

After testing out the sound of substitute bells, the broadcaster said it will use a recording.